Ultrasonographic findings of fluid accumulation and hyperechogenic spots suggestive of surgical site infection following laparotomy for colic in horses

Background: The aim of this study was to compare ultrasonographic findings of the ventral midline incision after exploratory laparotomy for colic in horses with and without surgical site infection (SSI). Methods: Ultrasonographic examination of the surgical wound was performed on postoperative day 5 (D5) and day 10 (D10) to assess the presence of fluid accumulation, suture sinus formation, hyperechogenic spots and fistulous path. Clinical evaluation of the wound was used to classify horses with and without SSI. The accuracy, sensitivity, specificity and positive and negative predictive values of the ultrasonographic findings were then calculated. Multivariable logistic regression analyses were performed with SSI as a dependent variable and age, sex, breed and ultrasonographic findings as independent variables after univariate and collinearity analyses. Results: Twenty-nine of the 84 horses examined had an SSI. Detection of fluid accumulation and hyperechogenic spots increased the odds for SSI at D5 (odds ratio [OR]: 4.99, 95% confidence interval [CI]: 1.53-16.33, p = 0.008; OR: 10.78, 95% CI: 1.75-26.59, p = 0.01, respectively) and D10 (OR: 11.51, 95% CI: 2.39-55.47, p = 0.002; OR: 12.34, 95% CI: 3.45-44.15, p < 0.001, respectively). Limitation: Ultrasonographic images were taken only on the longitudinal section. Conclusion: Ultrasonographic examination is helpful in evaluating the surgical incision after laparotomy, with the detection of fluid accumulation and hyperechogenic spots surrounding the sutures being strongly related to SSI.